Multicast Handling in TRILL Interconnects via Rendezvous Points

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Solution Overview

Problem

In large data centers, conventional TRILL networks face performance degradation due to unfavorable border crossings during multicast data forwarding, caused by nickname translations across RBridge areas, leading to unmanageable table sizes and inefficient packet handling.

Innovation Solution

Implementing a Boot Strap RBridge (BSR) approach to select rendezvous points between Layer 1 and Layer 2 network areas, creating a global tree structure with unique nicknames for multicast trees, and using periodic announcements to ensure proper loop-free forwarding and reduce nickname translations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If conventional TRILL networks use nickname translations at border RBridges for multicast forwarding, then multicast data can be forwarded across different network areas, but performance degradation occurs due to unfavorable border crossings and extensive nickname translations

Engineering Contradiction:

Improvemulticast forwarding capabilityVSAvoidpacket forwarding performance

Core Design Contradiction:

Ease of operationVSProductivity

Solution Approach 1:

The patent introduces a Rendezvous Point (RP) RBridge as an intermediary entity that receives multicast data packets and forwards them to destination RBridges. This intermediary approach eliminates the need for border RBridges to perform extensive nickname translations, as the RP RBridge handles the forwarding using its local knowledge of destination RBridges, thereby improving packet forwarding performance while maintaining multicast capability across network areas.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Quantity of substance

If TRILL networks scale upward in size to accommodate more devices, then network capacity increases, but forwarding table sizes become unmanageable

Engineering Contradiction:

Improvenetwork device capacityVSAvoidforwarding table size

Core Design Contradiction:

Quantity of substanceVSDevice complexity

Solution Approach 1:

The patent segments the large TRILL network into multiple network areas, each managed by area RBridges. The Rendezvous Point (RP) RBridge maintains forwarding information for destination RBridges in a structured manner, organizing the network hierarchy into areas and borders. This segmentation allows the network to scale to accommodate more devices while keeping individual forwarding tables manageable by distributing the forwarding state across multiple RBridges rather than requiring a single monolithic table.

Inventive Principle:

Principle #1Segmentation

3Adaptability or versatility

If border RBridges perform nickname translations for multicast traffic, then traffic can cross network area borders, but the translation process causes performance degradation

Engineering Contradiction:

Improvecross-area traffic routingVSAvoidpacket handling efficiency

Core Design Contradiction:

Adaptability or versatilityVSProductivity

Solution Approach 1:

The patent implements preliminary action by having the Rendezvous Point (RP) RBridge pre-establish knowledge of destination RBridges and their locations within network areas. Instead of performing nickname translations at the border during packet forwarding, the RP RBridge uses its pre-computed forwarding information to directly forward packets to destination RBridges. This preliminary preparation of routing information eliminates the need for real-time nickname translations, thereby improving packet handling efficiency while maintaining cross-area routing capability.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS9391799B2Multicast handling in a transparent interconnect of lots of links based data center interconnect

Publication Date: 2016.07.12 CISCO TECHNOLOGY INC

AI summary

In some embodiments, a global tree structure identifying rendezvous points between a layer 1 network area and a layer 2 network area may be created. When the rendezvous point receives a data packet associated with a destination for the layer 1 network area from the layer to network area, it may forward the data packet to the destination. Non-rendezvous point devices may discard copies of the data packet.